Aqueous dispersions of salicyl



when set). 25, 1947 f [unites STATES Parent OFFICE AQUEOUS msrnnsrons or SALICYL- V ANILIDE .i'oseph Edward Smith and Paul Jones Mitchell, J12, Wilmington, Del., assignors to E. I. du Pont de Nernours & Company, Wilmington, Del., a

corporation of Delaware No Drawing. Application January 20, 1944,

v 1 "This invention relates to the preparation of highly stable aqueous dispersions of salicylanilide and, more particularly, to thepreparation of highly stable aqueous dispersions of salicylanilide :using polyvinyl alcohol as the dispersing agent;

. This invention has as an object the preparation of highly stable aqueous dispersions of salicylanilide. A further object is the preparation of highly stable aqueous dispersions of salicylanilide using polyvinyl alcohol as the dispersing agent. A still further object is the preparation of highly stable aqueous dispersions of salicylanilide, compatible with both positively and negatively -.charged textile finishing materials. Other and furtherimportant objects of this invention will .appear as the description proceeds. These objects are accomplished by the followi-ng invention, in which a petroleum hydrocarbon is dispersed along with salicylanilide in a water solution of polyvinyl alcohol. Thus, an aqueous solution of. a partially saponified polyvinyl ace- ;tate is agitated vigorously with a refined petroleum hydrocarbon such as a mineral oil or wax,

obtained. Cationic surface active agents, water soluble metal salts of polyvalent metals, or various combinations of the two may be added during or after the preparation of the emulsion to impart a positive charge to the dispersed-particles.

Salicylanilide is well known in the art, and is ;used widely as a mildewproofing agent for textiles. The salicylanilide is usually applied by impregnating the textile with a solution thereof in aqueous ammonia or in an organic solvent, or with an aqueous dispersion of the agent. It is also known in the prior art to use salicylanilide in combination with separately prepared aqueous compositions containing wax and aluminum salts for producing combined water repellent, and mil- .dewproof effects. It is also known to use salicylanilide in combination with resin dispersions, starches, gums, clay, anionic and cationic surface active finishing agent-s, etc.

In the preferred practice, aqueous dispersions :of salicylanilide are generally prepared by the aid of protective colloids, such as polyvinyl alcohol, glue casein, water-soluble methyl cellulose, and deacetylated chitin acetate. The use of ionic dispersing agents or other materials which lower :the surface tension of water. at the water-air interface is generally avoided, since these usually at such a temperature that all phases are liquid,

. t0f*0bt8.llfl an aqueous emulsion of the wax or oil. Finely divided salicylanilicle is added and agitation continued until a homogeneous dispersion is have wetting properties, whereas-the, mildewpara in wax and 6 to 20 parts of pol in ihol f hllll Serial No. 519,040 6 Claims. (01. 1'6742) proofing treatment is often contemplated for application in combination with water-repellency treatments. However; while the protective colloids aforementioned will generally succeed in producing aqueous dispersions of good initial stability, the dispersions sediment markedly on storage for a few weeks and have inferior dispersibility on dilution with water. The sedimerited layer which develops on storage is diffi cult to redisperse with the equipment available 'in textile processing plants.

We have now found that aqueous dispersions of salicylanilide which have exceptionally good stability to storage over a period of months and excellent dispersibility in water can be prepared --using polyvinyl alcohol as the dispersing agent and a substantial amount of a refined mineral oil or paraffin wax as a stabilizer for the dispersion.

Satisfactory dispersions contain a minimum of approximately 10 parts of the mineralpil or parafin wax and-6 parts of polyvinyl alcohol for parts'of the Wmts r petroleum hydrocar on and polyvinyl alcohol greater than the minimum given above can be used without deleterious efiect on the dispersion stability and are limited only by such practical considerations as the viscosity of the dispersion and its salicylanilide content. If too high a concentration of polyvinyl alcohol is present, the dispersion is not suflicientiy fluid to be free flowing. Generally speaking, dispersions suitable for marketing contain 10 to 45% solids; dispersions of higher concentration can be made but they are not as readily diluted with water or as easily handled because of their high viscosity. Consein saponification number from 0 to 250. The Viscosity of these polyvinyl alcohols in aqueoussolu tion may vary from about 5 to 55 centipoises for 9.4% solution at 20 C. The viscosity of the polyvinyl alcohol in solution is related to. the mo- :lecular weight or thepolyvinyl ester from which in any way.

it is obtained. In practicing this invention, it is preferred to use polyvinyl alcohols varying in saponification number in the range 80 to 245 and giving a viscosity in a 4% aqueous solution at 20 C. of 20 to 40 centipoises. It may be advantageous to purify the polyvinyl alcohol solution before use by a treatment with activated charcoal and diatomaceous earth as described in copending application of Joseph Edward Smith, Serial No. 471,577 (Patent No. 2,368,949, issued February 6, 1945).

It is preferred to prepare the compositions of this invention by emulsifying the paraflin wax or mineral oil in the polyvinyl alcohol solution and then adding the pulverized salicylanilide. However, the order of mixing is not critical and can be varied by first dispersing the salicylanilide in the polyvinyl alcohol solution followed'by the mineral oil or paraflin wax. The salicylanilide can be mixed with the mineral oil or melted wax and the mixture added to the polyvinyl alcohol solution. Other materials such as aluminum acetate, aluminum formate or cationic surface active agents, added to impart a positive charge to the dispersion, canbe incorporated at any stage of the operation.

The emulsification and dispersion. of the oils, ,waxes, and salicylanilide can be carried out in any of the common colloid mills in which the emulsifying and dispersing action is accompanied by high turbulence. The temperature must be such that the oils and waxes are in the liquid state during the emulsification process, and may vary between room temperature and 95 C. The salicylanilide is prepared for use by a micropul- -verizing operation to obtain an average particle size oi to 20 microns. The salicylanilide remains as a solid throughout the manufacturing process.

The following examples are given to illustrate the invention but are not intended to limit it Example 1 30 parts of a textile finishing blended mineral oil having a viscosity of 100 S. U. V. at 100 .are added to a solution of 9 parts of polyvinyl alcohol dissolved in 101 parts of water at 30 C.,

while agitating with a, Hamilton-Beach highspeed stirrer such as is used at soda fountains. .The polyvinyl alcohol has a saponification number of 110 and produces a 4% aqueous solution ,having a viscosity of about 20 centipoises at 20 C. After agitating for 3 minutes to obtain an emulsion of the mineral oil, 60 parts of pulverized salicylanilide having a particle size of 10 to v20 microns are added to the emulsion. Agitation is continued for seven minutes to obtain a homogeneous, fluid, aqueous dispersion. The dispersion does not sediment on storage for six months.

A polyvinyl alcohol with a saponification number of 180 and which produces a 4% aqueous solution having a viscosity of about 40 centipoises can be substituted in the above example to obtain a dispersion of equivalent stability.

Example 2 30 parts of a crude scale parafiin wax (M. P. 51-52 C.) are added to a solution of parts -of polyvinyl alcohol dissolved in 235 parts of water at 80 C. while agitating with a Hamilton- ..Beach high-speed mixer. The polyvinyl alcohol has a saponification number of 110 and produces -a 4% aqueous solution having a viscosity-of about 4 centipoises at 20 C. After agitating for 3 minutes to obtain an emulsion of the wax, 120 parts of finely divided salicylanilide with an average particle size of 10 to 20 microns are added. Agitation is continued for about 10 minutes to obtain a completely homogeneous product. The dispersion is cooled to room temperature. A

' highly stable, aqueous dispersion is obtained departing from the spirit of this invention.

'cylanilide.

which does not sediment on storage for 6 months.

A polyvinyl alcohol with a saponification num-- ber of and which produces a 4% aqueous solution having a viscosity of about 40 centipoises can be substituted for the polyvinyl alcohol described in the above example to obtain an aqueous dispersion of equivalent stability.

' Example 3 20 minutes, while simultaneously passing the mixture through a disc type homogenizing pump to obtain an emulsion with an average particle size of l to 3 microns. 120 parts of finely divided salicylanilide with an average particle size of 10 -to 20 microns are added. Agitation is continued for about 45 minutes to obtain a completely homogeneous product. The dispersion is cooled to room temperature. A highly stable aqueous dispersion is obtained which does not sediment on storage for 6 months.

The compositions of Examples land 2 are compatible with both anionic and cationic surface active agents and finishing compositions. The composition of Example 3 is compatible with cationic or positively charged surface active agents and finishes only.

It will be clear that the details hereinabove se forth may be varied within wide limits without Thus, other types of refined petroleum oils and petroleum hydrocarbon waxes, either of the parafiinic or oycloaliphatic types or mixtures of the same, may be substituted for those specifically disclosed in the above examples. Those refined petroleum hydrocarbons having a boiling point above C. are preferred.

Very high stability of salicylanilide dispersions prepared with polyvinyl alcohol is achieved by incorporating 1 part. of paraffin wax or refined mineral oil for 4 parts of salicylanilide in the dispersions. Substantially improved results are obtained using as little as 1 part of paraflin wax or mineral oil for 10 parts of salicylanilide.

The invention has as an advantage the preparation of highly stable aqueous dispersions of sali- The dispersions remain uniformly stable on storage over a period of at least six months as required for commercial distribution. The dispersions prepared have wide utility in that a single product can be obtained that is compatible with both positively or negatively charged emulsions, dispersions and surface active materials used as finishing agents.

We claim as our invention:

1 A mildewproofing agent for textile fiber,

comprising salicylanilide dispersed in water by the aid of a water-soluble polyvinyl alcohol-having dispersing qualities, and stabilized by the aidof a saturated aliphatic hydrocarbon which has a boiling range above 110 C., the entire dispersion containing not less than total solids by weight.

2. A composition of matter comprising an aqueous dispersion of salioylanilide, a polyvinyl alcohol and a saturated aliphatic hydrocarbon Whose boiling range is above 110 (3., the proportion of the hydrocarbon being not less than 10 parts by weight, and that of the polyvinyl alcohol not less than 6 parts by Weight, per 100 parts of salicylanilide; the entire dispersion containing from 10 to 45% total solids by weight, and said polyvinyl alcohol being a partially saponlified polyvinyl acetate having a saponification number between 80 and 245 and yielding, when diluted with water to 4% concentration, a solution whose viscosity at C. is between 20 and centipoises.

3. A composition of matter as in claim 2, the

aliphatic hydrocarbon being a refined parafin wax and being present in quantity of from 25 to parts by weight per parts of salicylanilide, and the latter constituting about 30% by weight of the entire composition. 4. A composition of matter as in claim 2, the polyvinyl alcohol being present in quantity of from 6 to 20 parts by weight per 100 'parts of salicylanilide, and the latter constituting about 30% by weight of the entire composition.

5. A composition of matter for treating textile fiber, comprising substantially 120 parts of saliycylanilide, 5 parts of basic aluminum iormate, 30

parts of a parafin wax melting at about 55 C., and 15 parts of a polyvinyl alcohol having a saponification number of about and producing, when diluted with water at 20 C. to a concentration of 4%, an aqueous solution of 20 centipoises viscosity; said ingredients being jointly suspended in water in the form of a stable dispersion and constituting about 42% by weight of the entire composition.

6. The method of stabilizing a concentrated aqueous dispersion of salicylanilide and polyvinyl alcohol in water, which comprises incorporating in said dispersion a saturated aliphatic hydrocarbon of boiling point not less than 110 C. and in quantity not less than 0.1 of the weight of the salicylanilide, the salicylanilide being micropulverized prior to incorporation, and the incorporation step being carried out at a temperature at which said saturated aliphatic hydrocarbon is liquid.

JOSEPH EDWARD SMITH. PAUL J ONES MITCHELL, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name .Date

2,277,788 Shipp et a1. Mar. 31, 1942 1,873,365 Fargher et a1 Aug. 23, 1932 

